Ravens Know What Hidden Thieves Are Thinking

The genus Corvus contains some decidedly clever birds. Ravens, for example, have been shown to remember cheaters, those that take more than their fair share of food. Now, a new piece of research has suggested that they are also able to understand the motives of others within their group. This study, published in Nature Communications, concludes that the ability to think abstractly about the minds of others isn’t unique to primates.

Imagining what another animal is seeing is a component of the Theory of Mind (ToM) – the general ability to understand what others are thinking. This is one of the key ways that humans, chimpanzees, and monkeys operate in their own societies. A team of researchers led by the University of Vienna wanted to find out if ToM applies to ravens.

When ravens are being watched, they hide food more quickly, and they tend to construct multiple caches – this way, a competitor won’t be able to find out where they are concealing all their food. Although it’s clear that ravens are aware that their supply is at risk of being stolen, researchers were never sure whether they can actually preempt the malevolent intent of other ravens, or if they are merely using visual clues to predict their mischievous behavior.

With this in mind, an experiment was set up that, during the final stages, only allowed the ravens to detect the presence of another through audio cues. This study used two rooms, both connected by windows, which could be variably open or covered up. Additional peepholes provided a connection between the two rooms, which could also be open or closed.

In the first experiment, one raven was placed in each room, but only one was given food. As expected, with the window open, the raven with food rapidly buried it and then moved away from the hidden cache. In the second experiment, the ravens were trained to look through the peepholes in order to watch a human making caches of food in the room next door. This allowed the ravens to realize that they could be observed by others through the peephole.

Ravens appear to have at least the visual component of ToM. Marcin Perkowski/Shutterstock

Next, the researchers covered up the windows, left the peephole open, and gave the raven in one room some food to bury. There was no raven in the other room, but the researchers played raven calls through a speaker towards the open peephole. The ravens in this setup buried the food in roughly eight seconds.

Finally, when the peephole and window were both covered up, but with raven noises coming from the next room, the ravens concealed their resources within 14 seconds, and returned more often to the same cache.

This indicates that if they feel they are being watched, even if they cannot see any other ravens, they act more cautiously for fear of being robbed. When they know they cannot be seen, even if they can hear another raven nearby, they feel safer and act less carefully.

This indicates that ravens can imagine the thieving intents of others by considering what a competitor might see, an important component of ToM. Thomas Bugnyar, lead author of the study, told New Scientist that this “means that some non-human animals can…[attribute] a mental state to another one, which has always been considered to be one of the unique human abilities.”